The long term goal is to explore the potential of a novel class of compounds with a unique mechanism of action different from existing antiviral drugs for the treatment of hepatitis B (HBV). HBV is an infectious agent that infects the liver and causes severe consequences, such as liver failure, fibrosis, cirrhosis and hepatocellular carcinoma. All the approved chemotherapeutic treatments (i.e. Lamivudine, Adefovir and Entecavir) only inhibit viral replication by interfering viral DNA synthesis. Resistant variants which develop due to viral DNA polymerase mutation invariably emerge with long-term treatment. Therefore, novel compounds with mechanisms other than the action on viral DNA polymerase, working alone or in combination with current treatments, are needed. A series of derivatives from the natural product, Helioxanthin, were synthesized and discovered to perform a wide-spectrum of antiviral activity by us. Two derivatives, 8-1 and 5-4-2, exhibited potent anti-HBV activity in culture. Unlike the current clinically used anti-HBV drugs that only inhibited HBV DNA synthesis, 8-1 and 5-4-2 inhibit HBV DNA, RNA, and proteins as determined in HBV stably transfected cell lines. HBV resistant to Lamivudine was still sensitive to these compounds. The action of 8-1 and 5-4-2 is different from other anti-HBV drugs and has never been reported. The mechanism of action seems to involve direct alteration of the viral transcription complex. In this application two specific aims are proposed as following: 1. Study of the unique mechanism of the antiviral action of 8-1 and 5-4-2 against HBV. This includes: the mechanism against HBV RNA transcription, potentiation of anti-HBV activity nucleoside drugs, activity against HbeAg- HBV, and uptake and metabolism in HBV infected cells. 2. Evaluation of the in vivo anti-HBV activity of 8-1. Compound 5-4-2 will be the backup compound. A novel HBV transgenic mice will be used to obtain preliminary pharmacokinetic information and toxicity of 8-1 as well as to assess antiviral activity of 8-1. The studies proposed will provide information about not only the potential of the novel compound 8-1, as an anti-HBV drug, but also the roles of liver enriched transcription factors in regulation of HBV transcription.